<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
<script>
	var str="Hello world!"
document.write(str.substring(3))		//	lo world! 

var str = 'abcdef';
alert(str.substring(2));		//	cdef
</script>
</body>
</html>